System-Level Refrigeration Cycle (2P)
System-level, two-phase refrigeration block in a moist air, thermal liquid, or two-phase fluid network
Since R2023a
Libraries:
Simscape /
Fluids /
Two-Phase Fluid /
Thermodynamic Cycles
Description
The System-Level Refrigeration Cycle (2P) block models a basic refrigeration cycle consisting of a compressor, a condenser, a liquid receiver, a thermostatic expansion valve, and an evaporator. The block models the refrigerant loop within the block in the two-phase fluid domain using the fluid properties specified at port F. The condenser and evaporator external fluids can be part of a moist air, thermal liquid, or two-phase fluid network. The external fluids are the fluids in the condenser and evaporator opposite the refrigerant.
When the compressor is on, the refrigeration cycle consumes power to transfer heat from the evaporator external fluid to the condenser external fluid. The subcomponents provide the specified nominal heat transfer under nominal operating conditions.
Block Structure
This block behaves as a simplified version of this refrigeration cycle made from Simscape™ Fluids™ blocks that model the condenser, compressor, evaporator, expansion device, and liquid receiver:
The refrigerant flows through the loop counterclockwise. The compressor, which is controlled by the signal at port S, sucks in refrigerant vapor and produces a hot, high-pressure vapor, which moves to the condenser. The condenser rejects heat from the refrigerant to the external fluid to condense the refrigerant. The liquid receiver acts as a storage tank for the refrigerant and only allows liquid flow to exit, which helps maintain normal operation even if fluctuating external conditions cause the condenser output to vary. From the tank, the refrigerant flows to the expansion device, which is typically a valve or capillary tube that produces a large pressure loss. The drop in pressure partially vaporizes the refrigerant, which chills it. The refrigerant moves to the evaporator, which absorbs heat from the external fluid to the cold refrigerant to vaporize the refrigerant.
The subcomponents of the System-Level Refrigeration Cycle (2P) block behave the same as these Simscape Fluids blocks in this model, but the equations for the positive displacement compressor, expansion valve, receiver component, and condenser and evaporator subcomponents vary. For more information on the individual components of a refrigeration system, see:
The compressor and evaporator components depend on the External fluid for condenser heat transfer and External fluid for evaporator heat transfer parameters. For more information, see:
The compressor subcomponent determines the refrigerant mass flow rate for the system. The
physical signal input port S controls the compressor
operation. When the value at port S is
0
, the compressor is off and the mass flow rate is
0
. When the value at port S is
1
, the compressor runs at the nominal shaft speed, which
produces the nominal mass flow rate under nominal operating conditions. To
prevent reverse flow, the value of S must be greater than
or equal to 0
.
The mass flow rate in the compressor is
where:
ηv is the volumetric efficiency.
S is the value of the signal at port S.
vin is the inlet specific volume.
is the nominal volumetric flow rate, which the block determines from the nominal mass flow rate, , which depends on the setting of the Capacity specification parameter:
When the Capacity specification parameter is
Cooling load
,where Qcooling is the Nominal evaporator heat transfer parameter, h1 is the evaporator outlet specific enthalpy, and h4 is the valve outlet specific enthalpy.
When the Capacity specification parameter is
Heating load
,where Qcooling is the Nominal condenser heat transfer parameter, h2 is the compressor outlet specific enthalpy, and h3 is the condenser outlet specific enthalpy.
When the Capacity specification parameter is
Refrigerant mass flow rate
, is the value of the Nominal mass flow rate parameter.
The fluid power that the compressor adds to the flow is
where:
hout,isem is the specific enthalpy evaluated at the output pressure for an isentropic process.
hin is the inlet specific enthalpy.
ηs is the isentropic efficiency.
When Performance specification is
Coefficient of performance for cooling
orCoefficient of performance for heating
, the block solves for ηs by calculating h2 and using the relationwhere h2isen is the compressor outlet specific enthalpy assuming an isentropic process.
When Performance specification is
Coefficient of performance for cooling
, the block solves for h2 with where CoPcooling is the Coefficient of performance at nominal conditions parameter.When Performance specification is
Coefficient of performance for heating
, the block solves for h2 with where CoPheating is the Coefficient of performance at nominal conditions parameter.
When Performance specification is
Compressor isentropic efficiency
, ηs is the value of the Compressor isentropic efficiency parameter.
The block calculates the volumetric efficiency directly from the inlet and outlet specific volumes
where:
C is the clearance volume fraction that the block determines from the nominal operating conditions.
vin and vout are the inlet and outlet specific volumes evaluated at the inlet and outlet pressures.
The compressor subcomponent does not have mechanical rotational ports and does not need to calculate shaft torque. The mechanical power is
where ηm is the mechanical efficiency.
The relationship between mass flow rate, which the compressor determines, and the pressure drop across the thermostatic expansion valve subcomponent is
where:
vin is the inlet specific volume.
Δp is the pressure differential over the valve.
Δplam is the pressure threshold for transitional flow. Below this value, the flow is laminar.
The effective valve area depends on the pressure difference between the measured pressure, pbulb, and the equalization pressure, peq
where:
β is a valve constant the block determines from the nominal operating conditions.
Tevap is the evaporating temperature, which depends on the Pressure specification setting:
When Pressure specification is
Pressure at specified saturation temperature
, Tevap is the value of the Nominal evaporating (saturation) temperature parameter.When Pressure specification is
Specified pressure
, Tevap is the saturation temperature that corresponds to the value of the Nominal evaporator pressure parameter.
ΔTstatic is the Static (minimum) evaporator superheat parameter.
psat(Tevap) is the fluid saturation pressure as a function of Tevap.
psat(Tevap+ΔTstatic) is the fluid saturation pressure as a function of Tevap+ΔTstatic.
pbulb is the fluid pressure of the bulb. This pressure is the saturation pressure at the evaporator outlet temperature.
peq is the equalization pressure, which is the evaporator pressure for this block.
The effective valve area has limits. The minimum effective valve area, Seff,min, is
where fleak is the value of the Ratio of leakage to nominal expansion valve opening parameter. The maximum effective valve area, Seff,mmax, is
where fmax is the value of the Ratio of maximum to nominal expansion valve opening parameter.
Excluding the receiver, the block assumes that the refrigerant mass flow rate is the same value through the loop. In the receiver, the total mass is based on the balance between the mass flow rate produced by the compressor and the mass flow rate metered by the expansion valve. The outflow from the receiver subcomponent is always liquid and perfectly insulated from the environment.
The liquid mass fraction in the receiver subcomponent is
where:
xliq is the liquid mass fraction.
liq,in is the portion of the flow in that is liquid.
out is the mass flow rate out of the receiver.
vaporization is the rate of vaporization from the liquid volume to the vapor volume.
condensation is the rate of condensation from the vapor volume to the liquid volume.
The pressure relates to the total mass via the specific volume using the relation
where:
V is the total receiver volume.
vliq is the is the specific volume of the liquid volume.
vvap is the is the specific volume of the vapor volume.
The condenser and evaporator subcomponents model the refrigerant thermal mass, but do not model fluid volume. For the condenser and evaporator, the energy conservation equation is
where:
M is the constant mass of refrigerant in the component.
hI is the refrigerant specific enthalpy at the component internal node.
is the refrigerant mass flow rate.
Q is the rate of heat transfer from the external fluid to the refrigerant.
hin and hout are the refrigerant specific enthalpy in and out of the component.
Visualize the P-H Diagram
To visualize the refrigeration cycle, use a Probe block from the Simscape > Utilities library to output the
variables p_cycle
and h_cycle
. These variables
contain the four pressure and specific enthalpy points of the refrigeration cycle.
Connect the variables to the P-H Diagram
(2P) block to visualize the refrigeration cycle.
This diagram shows the fluid attributes throughout the system for the refrigerant R-410a. Segment 1 to 2 is the compressor, segment 2 to 3 is the condenser, point 3 is the receiver, segment 3 to 4 is the expansion valve, and segment 4 to 1 is the evaporator.
Assumptions and Limitations
The block does not model reverse flow and limits the refrigeration cycle to zero and forward flow only. To prevent reverse flow, the block limits the compressor control to zero or forward operation and only models fluid volume in the liquid receiver subcomponent.
Excluding the liquid receiver, the subcomponents do not model refrigerant fluid volume, which prevents the accumulation of mass in subcomponents. As a result, the refrigerant mass flow rate is the same through the evaporator, compressor, and condenser subcomponents.
There is no refrigerant pressure loss in the evaporator or condenser.
The block does not model kinetic energy changes in the refrigerant flow.
The evaporator subcomponent models approximate pressure dynamics to maintain numerical robustness. However, the condenser subcomponent does not model approximate pressure dynamics, because the condenser pressure is equal to the receiver pressure, which does model pressure dynamics.
The condenser and evaporator subcomponents only model counter flow because the refrigerant is primarily in the two-phase mixture state within the condenser and evaporator. Consequently, the temperature is uniform across most of the condenser and evaporator, and there is no significant difference between counter flow and cross flow.
When determining the heat exchanger size, the block ignores the values of the Fraction of condensate entrained as water droplets parameters and assumes that the condensate is not entrained as droplets.
Examples
Data Center Cooling
Models the cooling system of a data center. The system consists of two separate water loops: a chilled water loop and a condenser water loop. The chilled water loop absorbs heat from the server farm and transfers it to the condenser water loop. The condenser water loop rejects this heat to the environment using a cooling tower.
Refrigeration Cycle (System-Level)
Model a refrigeration cycle for a home air conditioning system at an abstract system level using the System-Level Refrigeration Cycle (2P) block. This block simplifies the set up of the refrigeration cycle by encapsulating the entire refrigerant loop in one block.
Refrigeration Cycle (Air Conditioning)
A refrigeration cycle for a home air conditioning system. See Model a Refrigeration Cycle for the recommended steps to build this model in the two-phase fluid domain.
Residential Refrigerator
Models a basic refrigeration system that transfers heat between the refrigerant two-phase fluid and the environment moist air mixture. The compressor drives the R134a refrigerant through a condenser, a capillary tube, and an evaporator. An accumulator ensures that only vapor returns to the compressor.
Ports
Input
S — Signal that operates compressor, unitless
physical signal
Physical signal input that operates the compressor. A value of
0
means the compressor is off. A value of
1
means the compressor is operating at the
nominal capacity.
Conserving
F — Refrigerant properties
two-phase fluid
Two-phase fluid conserving port associated with the refrigerant properties. Connect a Two-Phase Fluid Properties (2P) or Two-Phase Fluid Predefined Properties (2P) block to this port. Do not connect any other Two-Phase Fluid blocks to port F because this port acts as an absolute reference.
Ac — Condenser external fluid inlet
moist air | thermal liquid | two-phase fluid
Moist air, thermal liquid, or two-phase fluid conserving port associated with the condenser external fluid inlet. The block assumes that the condenser external fluid flows from port Ac to port Bc. The External fluid for condenser heat transfer parameter controls the port fluid.
Bc — Condenser external fluid outlet
moist air | thermal liquid | two-phase fluid
Moist air, thermal liquid, or two-phase fluid conserving port associated with the condenser external fluid outlet. The block assumes that the condenser external fluid flows from port Ac to port Bc. The External fluid for condenser heat transfer parameter controls the port fluid.
Ae — Evaporator external fluid inlet
moist air | thermal liquid | two-phase fluid
Moist air, thermal liquid, or two-phase fluid conserving port associated with the evaporator external fluid inlet. The block assumes that the evaporator external fluid flows from port Ae to port Be. The External fluid for evaporator heat transfer parameter controls the port fluid.
Be — Evaporator external fluid outlet
moist air | thermal liquid | two-phase fluid
Moist air, thermal liquid, or two-phase fluid conserving port associated with the evaporator external fluid outlet. The block assumes that the evaporator external fluid flows from port Ae to port Be. The External fluid for evaporator heat transfer parameter controls the port fluid.
Output
Qc — Heat rejected in condenser, W
physical signal
Physical signal output port that measures the heat rejected by the refrigerant in the condenser, in W.
Qe — Heat absorbed in evaporator, W
physical signal
Physical signal output port that measures the heat absorbed by the refrigerant in the evaporator, in W.
Pwr — Mechanical power consumed by the compressor, W
physical signal
Physical signal output port that measures the mechanical power consumed by the compressor, in W.
W — Rate of condensation in evaporator, kg/s
physical signal
Physical signal output port that measures rate of condensation in the evaporator
external fluid, in kg/s, if the External fluid for evaporator
heat transfer parameter is Moist
air
. If the External fluid for evaporator
heat transfer parameter is not moist air, this port
outputs 0
. The value of this port does not include
the portion of condensation that is entrained as water droplets.
Parameters
Refrigeration Cycle
Capacity specification — Method for specifying size of system
Cooling load
(default) | Heating load
| Refrigerant mass flow rate
Method for specifying the size of the system. You can specify the cooling load, heating load, or the refrigerant mass flow rate.
Nominal condenser heat transfer — Rate of heat transfer in condenser
15
kW
(default) | positive scalar
Rate of heat transfer from the refrigerant to the external fluid in the condenser.
Dependencies
To enable this parameter, set Capacity
specification to Heating
load
.
Nominal evaporator heat transfer — Rate of heat transfer in evaporator
15
kW
(default) | positive scalar
Rate of heat transfer from the external fluid to the refrigerant in the evaporator.
Dependencies
To enable this parameter, set Capacity
specification to Cooling
load
.
Nominal mass flow rate — Refrigerant mass flow rate
0.005
kg/s
(default) | positive scalar
Refrigerant mass flow rate through the cycle.
Dependencies
To enable this parameter, set Capacity
specification to Refrigerant mass flow
rate
.
Pressure specification — Method for specifying condenser and evaporator pressure
Specified pressure
(default) | Pressure at specified saturation
temperature
Method for providing condenser and evaporator pressures. Select whether to directly provide the pressures or provide the corresponding saturation temperatures.
Nominal condenser pressure — Refrigerant pressure in condenser
1
MPa
(default) | positive scalar
Pressure of refrigerant in the condenser.
Dependencies
To enable this parameter, set Pressure
specification to Specified
pressure
.
Nominal evaporator pressure — Refrigerant pressure in evaporator
0.1
MPa
(default) | positive scalar
Pressure of refrigerant in the evaporator.
Dependencies
To enable this parameter, set Pressure
specification to Specified
pressure
.
Nominal condensing (saturation) temperature — Condenser refrigerant saturation temperature
333.15
K
(default) | positive scalar
Saturation temperature of refrigerant in the condenser.
Dependencies
To enable this parameter, set Pressure
specification to Pressure at specified
saturation temperature
.
Nominal evaporating (saturation) temperature — Evaporator refrigerant saturation temperature
273.15
K
(default) | positive scalar
Saturation temperature of refrigerant in the evaporator.
Dependencies
To enable this parameter, set Pressure
specification to Pressure at specified
saturation temperature
.
Nominal condenser subcooling — Operational condenser outlet temperature differential
5
deltaK
(default) | positive scalar
Degrees of temperature below saturation temperature at the condenser outlet.
Nominal (static + opening) evaporator superheat — Operational evaporator outlet temperature differential
10
deltaK
(default) | positive scalar
Degrees of temperature above saturation temperature at the evaporator outlet. The expansion valve adjusts its valve area to try to maintain this superheat.
Static (minimum) evaporator superheat — Minimum allowable temperature differential at evaporator outlet
5
deltaK
(default) | positive scalar
Superheat threshold to close the expansion valve.
Performance specification — Method to specify refrigeration cycle efficiency
Coefficient of performance for
cooling
(default) | Coefficient of performance for
heating
| Compressor isentropic efficiency
Method to specify the refrigeration cycle efficiency. Choose based on the coefficient of performance of the cycle for heating, cooling, or the compressor efficiency.
Coefficient of performance at nominal conditions — Ratio of cooling or heating to power consumed for compressor
3
(default) | positive scalar
Ratio of useful cooling or heating by the refrigeration cycle to the power consumed by the compressor.
Dependencies
To enable this parameter, set Performance
specification to Coefficient of
performance for cooling
or
Coefficient of performance for
heating
.
Compressor isentropic efficiency — Ratio of ideal-to-actual change in specific enthalpy across compressor
0.8
(default) | positive scalar
Ratio of ideal, or isentropic, change in specific enthalpy to the actual change in specific enthalpy across the compressor.
Dependencies
To enable this parameter, set Performance
specification to Compressor isentropic
efficiency
.
Compressor volumetric efficiency at nominal conditions — Ratio of volumetric flow rate to displacement rate
0.95
(default) | positive scalar
Ratio of actual volumetric flow rate to the displacement rate of the compressor.
Compressor mechanical efficiency — Efficiency of conversion to torque
0.95
(default) | positive scalar
Ratio of the power delivered to the fluid flow to the power driving the mechanical shaft.
Ratio of maximum to nominal expansion valve opening — Ratio of open valve areas to maintain superheat
1.5
(default) | positive scalar
Ratio of the fully opened valve area to the valve area needed to maintain superheat at nominal conditions.
Ratio of leakage to nominal expansion valve opening — Ratio of closed valve areas to maintain superheat
1e-6
(default) | positive scalar
Ratio of the closed valve area to the valve area needed to maintain superheat at nominal conditions
Expansion valve smoothing factor — Numerical smoothing factor
0.01
(default) | positive scalar
Smoothing factor that introduces a layer of gradual change to the flow response when the valve is in near-open or near-closed positions. Set this value to a nonzero value less than one to increase the stability of your simulation in these regimes.
Condenser refrigerant volume — Volume of condenser refrigerant
0.001
m^3
(default) | positive scalar
Volume of refrigerant in the condenser.
Evaporator refrigerant volume — Volume of evaporator refrigerant
0.001
m^3
(default) | positive scalar
Volume of refrigerant in the evaporator.
Liquid receiver tank volume — Volume of liquid and vapor phases in receiver tank
0.01
m^3
(default) | positive scalar
Total physical volume of liquid receiver tank, including both the volume of liquid and vapor phases.
Initial receiver liquid level — Initial liquid volume fraction in tank
0.5
(default) | positive scalar
Liquid volume fraction in the receiver tank at the start of simulation.
Initialize refrigerant to nominal operating conditions — Whether to specify refrigerant initial conditions
on
(default) | off
Whether refrigerant in the cycle starts simulation at the nominal operating conditions based on the nominal operating parameters or specified explicitly with initial condition parameters.
Initial condenser pressure — Initial refrigerant pressure in condenser
1
MPa
(default) | positive scalar
Pressure of the refrigerant in the condenser and liquid receiver at the start of simulation.
Dependencies
To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.
Initial evaporator pressure — Initial refrigerant pressure in evaporator
0.1
MPa
(default) | positive scalar
Pressure of the refrigerant in the evaporator at the start of simulation.
Dependencies
To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.
Initial condenser specific enthalpy [inlet, outlet] — Initial refrigerant specific energy in condenser
[450, 250]
kJ/kg
(default) | positive scalar | two-element vector
Specific enthalpy of the refrigerant in the condenser at the start of simulation. If you specify this parameter as a vector of two values, the first element is the inlet specific enthalpy value and the second element is the outlet specific enthalpy value. If you enter a scalar, the block assumes that the inlet and outlet specific enthalpy are the same value.
Dependencies
To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.
Initial evaporator specific enthalpy [inlet, outlet] — Initial refrigerant specific energy in evaporator
[250, 400]
kJ/kg
(default) | positive scalar | two-element vector
Specific enthalpy of the refrigerant in the evaporator at the start of simulation. If you specify this parameter as a vector of two values, the first element is the inlet specific enthalpy value and the second element is the outlet specific enthalpy value. If you enter a scalar, the block assumes that the inlet and outlet specific enthalpy are the same value.
Dependencies
To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.
Initial receiver liquid and vapor fully saturated — Whether to specify receiver initial conditions
on
(default) | off
Whether the receiver starts the simulation at the saturation equilibrium, meaning the liquid and vapor volumes are both at the saturated state, or uses explicitly specified initial conditions.
Dependencies
To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.
Initial receiver liquid specific enthalpy — Receiver initial liquid specific enthalpy
500
kJ/kg
(default) | positive scalar
Specific enthalpy of the liquid portion of the refrigerant in the receiver at the start of simulation.
Dependencies
To enable this parameter, clear the Initialize refrigerant to nominal operating conditions and Initial receiver liquid and vapor fully saturated check boxes.
Initial receiver vapor specific enthalpy — Receiver initial vapor specific enthalpy
3500
kJ/kg
(default) | positive scalar
Specific enthalpy of the vapor portion of the refrigerant in the receiver at the start of simulation.
Dependencies
To enable this parameter, clear the Initialize refrigerant to nominal operating conditions and Initial receiver liquid and vapor fully saturated check boxes.
Condenser External Fluid
External fluid for condenser heat transfer — External fluid for heat transfer in condenser
Moist air
(default) | Thermal liquid
| Two-phase fluid
External fluid for heat transfer in the condenser.
Nominal mass flow rate — Mass flow rate between condenser ports
0.5
kg/s
(default) | positive scalar
Mass flow rate from port Ac to port Bc during nominal operating conditions.
Nominal pressure drop — Pressure drop between condenser ports
0.001
MPa
(default) | positive scalar
Pressure drop from port Ac to port Bc during nominal operating conditions.
Pressure specification — Method of pressure specification
Specified pressure
(default) | Pressure at specified saturation
temperature
Method of pressure specification:
Specified pressure
— Specify the nominal inlet pressure.Pressure at specified saturation temperature
— Specify the nominal saturation temperature that corresponds to the inlet pressure.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
.
Nominal inlet pressure — Pressure at external fluid side inlet of condenser
0.101325
MPa
(default) | positive scalar
Pressure at the inlet of the condenser on the external fluid side of the heat exchanger during the nominal operating condition.
Dependencies
To enable this parameter, set either:
External fluid for condenser heat transfer to
Moist air
orThermal liquid
.External fluid for condenser heat transfer to
Two-phase fluid
, and set Pressure specification toSpecific pressure
.
Nominal saturation temperature — Nominal saturation temperature to specify pressure
400
K
(default) | positive scalar
Saturation temperature at the outlet of the condenser external fluid side of the heat exchanger during the nominal operating condition. The pressure in the condenser is the corresponding saturation pressure.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
and Pressure
specification to Pressure at specified
saturation temperature
.
Inlet condition specification — Method to describe inlet condition of fluid
Specific enthalpy
(default) | Temperature
| Vapor quality
Method the block uses to describe the inlet condition of the condenser external fluid at the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
.
Nominal inlet temperature — Temperature at condenser external fluid side inlet
400
K
(default) | positive scalar
Temperature at the inlet of the external fluid side of the condenser during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
and Initial condition
specification to
Temperature
.
Nominal inlet specific enthalpy — Specific enthalpy at condenser external fluid side inlet
500
kJ/kg
(default) | positive scalar
Specific enthalpy at the inlet of the external fluid side of the condenser during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
and Initial condition
specification to Specific
enthalpy
.
Nominal inlet vapor quality — Vapor quality at condenser external fluid side inlet
1
(default) | positive scalar
Vapor quality, defined as the mass fraction of vapor in a liquid-vapor mixture, at the inlet of the external fluid side of the condenser during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
and Initial condition
specification to Vapor
quality
.
Inlet humidity specification — Method to describe humidity level at condenser external fluid side inlet
Relative humidity
(default) | Specific humidity
| Mole fraction
| Humidity ratio
| Wet-bulb temperature
Method the block uses to describe the humidity level at the inlet during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
.
Nominal inlet relative humidity — Relative humidity at inlet
0.1
(default) | scalar in the range [0,1]
Relative humidity at the inlet of the external fluid side of the condenser during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and Inlet humidity
specification to Relative
humidity
.
Nominal inlet specific humidity — Specific humidity at inlet
0.01
(default) | scalar in the range [0,1]
Specific humidity, defined as the mass fraction of water vapor in a moist air mixture, at the inlet of the external fluid side of the condenser during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and Inlet humidity
specification to Specific
humidity
.
Nominal inlet water vapor mole fraction — Mole fraction of water vapor at inlet
0.01
(default) | scalar in the range [0,1]
Mole fraction of the water vapor in a moist air mixture at the inlet of the external fluid side of the condenser during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and Inlet humidity
specification to Mole
fraction
.
Nominal inlet humidity ratio — Humidity ratio at inlet
0.01
(default) | scalar in the range [0,1]
Humidity ratio, defined as the mass ratio of water vapor to dry air and trace gas, at the inlet of the external fluid side of the condenser during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and Inlet humidity
specification to Humidity
ratio
.
Nominal inlet wet-bulb temperature — Wet-bulb temperature at the start of simulation
287 K
(default) | positive scalar in the range [0,1]
Wet-bulb temperature at the inlet of the external fluid side of the condenser during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and Inlet humidity
specification to Wet-bulb
temperature
.
Inlet trace gas specification — Method to describe trace gas level at inlet
Mass fraction
(default) | Mole fraction
Method the block uses to describe the trace gas level at the external fluid side inlet of the condenser during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
.
Nominal inlet trace gas mass fraction — Mass fraction of trace gas at inlet
0.001
(default) | scalar in the range [0,1]
Mass fraction of trace gas in a moist air mixture at the inlet of the external fluid side of the condenser during the nominal operating condition.
The block ignores this parameter if the Trace gas
model parameter in the Moist Air
Properties (MA) block is
None
.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and Inlet trace gas
specification to Mass
fraction
.
Nominal inlet trace gas mole fraction — Mole fraction of trace gas at inlet
0.001
(default) | scalar in the range [0,1]
Mole fraction of the trace gas in a moist air mixture at the inlet of the external fluid side of the condenser during the nominal operating condition.
The block ignores this parameter if the Trace gas
model parameter in the Moist Air
Properties (MA) block is
None
.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and Inlet trace gas
specification to Mole
fraction
.
External fluid volume — Volume of fluid in condenser
0.1
m^3
(default) | positive scalar
Total volume of external fluid in the condenser.
Cross-sectional area at port Ac — Flow area at port Ac
0.01
m^2
(default) | positive scalar
Flow area at the condenser external fluid port Ac.
Cross-sectional area at port Bc — Flow area at port Bc
0.01
m^2
(default) | positive scalar
Flow area at the condenser external fluid port Bc.
Condenser wall thermal mass — Option to model condenser wall heat transfer
Off
(default) | On
Whether to include the temperature dynamics of the heat transfer surface.
Condenser wall mass — Condenser heat transfer mass
1
kg
(default) | positive scalar
Total mass of the condenser heat transfer surface.
Dependencies
To enable this parameter, select Condenser wall thermal mass.
Condenser wall specific heat — Specific heat of condenser transfer surface
490
J/(K*kg)
(default) | positive scalar
Specific heat of the condenser heat transfer surface.
Dependencies
To enable this parameter, select Condenser wall thermal mass.
Initialize to nominal operating conditions — Whether to specify condenser initial conditions
On
(default) | Off
Whether to start the simulation at the nominal operating condition or specify a different set of initial conditions using additional parameters.
Initial pressure — Fluid pressure at start of simulation
0.101325
MPa
(default) | positive scalar
Condenser external fluid pressure at the start of the simulation.
Dependencies
To enable this parameter, clear the Initialize to nominal operating conditions check box.
Initial fluid energy specification — Initial state of the condenser external fluid
Specific enthalpy
(default) | Temperature
| Vapor quality
| Vapor void fraction
| Specific internal energy
Quantity used to describe the initial state of the condenser external fluid.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
and clear the Initialize to
nominal operating conditions check box.
Initial temperature — Temperature at start of simulation
293.15
K
(default) | positive scalar | two-element vector
Temperature at the start of simulation. If the value is a scalar, then the block assumes that the initial temperature is uniform. If the value is a two-element vector, then the block assumes that the initial temperature varies linearly between the ports condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set either:
External fluid for condenser heat transfer to
Moist air
orThermal liquid
and clear the Initialize to nominal operating conditions check box.External fluid for condenser heat transfer to
Two-phase fluid
, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification toTemperature
.
Initial vapor quality — Vapor mass fraction at start of simulation
0.5
(default) | scalar in the range [0,1] | two-element vector
Condenser external fluid vapor quality, defined as the mass fraction of vapor in a liquid-vapor mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial vapor quality is uniform. If the value is a two-element vector, then the block assumes that the initial vapor quality varies between the condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
, clear the Initialize to nominal
operating conditions check box, and set
Initial fluid energy specification to
Vapor quality
.
Initial vapor void fraction — Vapor volume fraction at start of simulation
0.5
(default) | scalar in the range [0,1] | two-element vector
Condenser external fluid vapor void fraction, defined as the volume fraction of vapor in a liquid-vapor mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial vapor void fraction is uniform. If the value is a two-element vector, then the block assumes that the initial vapor void quality varies between the condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
, clear the Initialize to nominal
operating conditions check box, and set
Initial fluid energy specification to
Vapor void fraction
.
Initial specific enthalpy — Enthalpy per unit mass at start of simulation
1500
kJ/kg
(default) | positive scalar | two-element vector
Condenser external fluid specific enthalpy at the start of simulation. If the value is a scalar, then the block assumes that the initial specific enthalpy is uniform. If the value is a two-element vector, then the block assumes that the initial specific enthalpy varies between the condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
, clear the Initialize to nominal
operating conditions check box, and set
Initial fluid energy specification to
Specific enthalpy
.
Initial specific internal energy — Internal energy per unit mass at start of simulation
1500
kJ/kg
(default) | positive scalar | two-element vector
Condenser external fluid specific internal energy at the start of simulation. If the value is a scalar, then the block assumes that the initial specific internal energy is uniform. If the value is a two-element vector, then the block assumes that the initial specific internal energy varies between the condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Two-phase
fluid
, clear the Initialize to nominal
operating conditions check box, and set
Initial fluid energy specification to
Specific internal energy
.
Initial humidity specification — Method used to describe initial humidity level
Relative humidity
(default) | Specific humidity
| Mole fraction
| Humidity ratio
| Wet-bulb temperature
Method used to describe the initial humidity level in condenser external fluid.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and clear the Initialize to nominal
operating conditions check box.
Initial relative humidity — Relative humidity at start of simulation
0.5
(default) | scalar in the range [0,1] | two-element vector
Condenser external fluid relative humidity at the start of simulation. If the value is a scalar, then the block assumes that the initial relative humidity is uniform. If the value is a two-element vector, then the block assumes that the initial relative humidity varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
, clear the Initialize to nominal
operating conditions check box, and set
Initial humidity specification to
Relative humidity
.
Initial specific humidity — Specific humidity at start of simulation
0.01
(default) | scalar in the range [0,1] | two-element vector
Condenser external fluid specific humidity, defined as the mass fraction of water vapor in a moist air mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial specific humidity is uniform. If the value is a two-element vector, then the block assumes that the initial specific humidity varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
, clear the Initialize to nominal
operating conditions check box, and set
Initial humidity specification to
Specific humidity
.
Initial water vapor mole fraction — Mole fraction of water vapor at start of simulation
0.01
(default) | scalar in the range [0,1] | two-element vector
Mole fraction of the water vapor in the condenser external fluid at the start of simulation. If the value is a scalar, then the block assumes that the initial water vapor mole fraction is uniform. If the value is a two-element vector, then the block assumes that the initial water vapor mole fraction varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
, clear the Initialize to nominal
operating conditions check box, and set
Initial humidity specification to
Mole fraction
.
Initial humidity ratio — Humidity ratio at start of simulation
0.01
(default) | scalar in the range [0,1] | two-element vector
Condenser external fluid humidity ratio, defined as the mass ratio of water vapor to dry air and trace gas, at the start of simulation. If the value is a scalar, then the block assumes that the initial humidity ratio is uniform. If the value is a two-element vector, then the block assumes that the initial humidity ratio varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
, clear the Initialize to nominal
operating conditions check box, and set
Initial humidity specification to
Humidity ratio
.
Initial moist air wet-bulb temperature — Wet-bulb temperature at the start of simulation
287 K
(default) | positive scalar in the range [0,1]
Condenser wet-bulb temperature at the start of the simulation.
If the value is a scalar, then the block assumes that the initial wet-bulb temperature is uniform. If the value is a two-element vector, then the block assumes that the initial wet-bulb temperature varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
, clear the Initialize to nominal
operating conditions check box, and set
Initial humidity specification to
Wet-bulb temperature
.
Initial trace gas specification — Method to describe initial trace gas level
Mass fraction
(default) | Mole fraction
Method used to describe the trace gas level at the start of simulation.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and clear the Initialize to nominal
operating conditions check box.
Initial trace gas mass fraction — Mass fraction of trace gas at start of simulation
0.001
(default) | scalar in the range [0,1] | two-element vector
Mass fraction of trace gas in a moist air mixture at the start of simulation. If the value is a scalar, then the block assumes that the initial mass fraction is uniform. If the value is a two-element vector, then the block assumes that the initial mass fraction varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
The block ignores this parameter if the Trace gas
model parameter in the Moist Air
Properties (MA) block is
None
.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
, clear the Initialize to nominal
operating conditions check box, and set
Initial trace gas specification to
Mass fraction
.
Initial trace gas mole fraction — Mole fraction of trace gas at start of simulation
0.001
(default) | scalar in the range [0,1] | two-element vector
Mole fraction of the trace gas in a moist air mixture at the start of simulation. If the value is a scalar, then the block assumes that the initial mole fraction is uniform. If the value is a two-element vector, then the block assumes that the initial mole fraction varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.
The block ignores this parameter if the Trace gas
model parameter in the Moist Air
Properties (MA) block is
None
.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
, clear the Initialize to nominal
operating conditions check box, and set
Initial trace gas specification to
Mole fraction
.
Initial mass ratio of water droplets to moist air — Ratio of water droplets to moist air
0
(default) | positive scalar
Initial mass ratio of water droplets to moist air.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
and clear the Initialize to nominal
operating conditions check box.
Initial condenser wall temperature — Condenser surface temperature at simulation start
293.15
K
(default) | positive scalar | two-element vector
Heat transfer surface temperature at the start of simulation. If this value is a scalar, the block assumes that the initial temperature is uniform. If this value is a two-element vector, then the block assumes that the temperature varies linearly between ports Ac and Bc with the first element corresponding to Ac and second element corresponding to Bc.
Dependencies
To enable this parameter, clear the Initialize to nominal operating conditions and Condenser wall thermal mass check boxes.
Relative humidity at saturation — Relative humidity point of condensation
1
(default) | nonnegative scalar
Relative humidity point of condensation. Condensation occurs above this value. In most cases, this value is 1, which is equivalent to 100%. A value greater than 1 indicates a supersaturated vapor.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
.
Water vapor condensation time constant — Time scale for condensation
1e-3 s
(default) | positive scalar
Characteristic time scale at which an oversaturated moist air volume returns to saturation by condensing out excess humidity.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
.
Water droplets evaporation time constant — Time scale for evaporation
1e-3 s
(default) | positive scalar
Characteristic time scale at which water droplets evaporate to vapor.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
.
Fraction of condensate entrained as water droplets — Fraction of condensate in water droplets
1
(default) | scalar in the range [0,1]
Fraction of the condensate in the moist air that is entrained as water droplets.
Dependencies
To enable this parameter, set External fluid for
condenser heat transfer to Moist
air
.
Evaporator External Fluid
External fluid for evaporator heat transfer — External fluid for heat transfer in evaporator
Moist air
(default) | Thermal liquid
| Two-phase fluid
External fluid for heat transfer in the evaporator.
Nominal mass flow rate — Mass flow rate between evaporator ports
0.5
kg/s
(default) | positive scalar
Mass flow rate from port Ae to port Be during nominal operating conditions.
Nominal pressure drop — Pressure drop between evaporator ports
0.001
MPa
(default) | positive scalar
Pressure drop from port Ae to port Be during nominal operating conditions.
Pressure specification — Method of pressure specification
Specified pressure
(default) | Pressure at specified saturation
temperature
Method of pressure specification:
Specified pressure
— Specify the nominal inlet pressure.Pressure at specified saturation temperature
— Specify the nominal saturation temperature that corresponds to the inlet pressure.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
.
Nominal inlet pressure — Pressure at external fluid side inlet of evaporator
0.101325
MPa
(default) | positive scalar
Pressure at the inlet of the evaporator on the external fluid side of the heat exchanger during the nominal operating condition.
Dependencies
To enable this parameter, set either:
External fluid for evaporator heat transfer to
Moist air
orThermal liquid
.External fluid for evaporator heat transfer to
Two-phase fluid
, and set Pressure specification toSpecific pressure
.
Nominal saturation temperature — Nominal saturation temperature to specify pressure
400
K
(default) | positive scalar
Saturation temperature at the outlet of the evaporator external fluid side of the heat exchanger during the nominal operating condition. The pressure in the evaporator is the corresponding saturation pressure.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
and Pressure
specification to Pressure at specified
saturation temperature
.
Inlet condition specification — Method to describe inlet condition of fluid
Specific enthalpy
(default) | Temperature
| Vapor quality
Method the block uses to describe the inlet condition of the evaporator external fluid at the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
.
Nominal inlet temperature — Temperature at evaporator external fluid side inlet
400
K
(default) | positive scalar
Temperature at the inlet of the external fluid side of the evaporator during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
and Initial condition
specification to
Temperature
.
Nominal inlet specific enthalpy — Specific enthalpy at evaporator external fluid side inlet
500
kJ/kg
(default) | positive scalar
Specific enthalpy at the inlet of the external fluid side of the evaporator during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
and Initial condition
specification to Specific
enthalpy
.
Nominal inlet vapor quality — Vapor quality at evaporator external fluid side inlet
1
(default) | positive scalar
Vapor quality, defined as the mass fraction of vapor in a liquid-vapor mixture, at the inlet of the external fluid side of the evaporator during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
and Initial condition
specification to Vapor
quality
.
Inlet humidity specification — Method to describe humidity level at evaporator external fluid side inlet
Relative humidity
(default) | Specific humidity
| Mole fraction
| Humidity ratio
| Wet-bulb temperature
Method the block uses to describe the humidity level at the inlet during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Moist
air
.
Nominal inlet relative humidity — Relative humidity at inlet
0.1
(default) | scalar in the range [0,1]
Relative humidity at the inlet of the external fluid side of the evaporator during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
and
Inlet humidity specification to
Relative humidity
.
Nominal inlet specific humidity — Specific humidity at inlet
0.01
(default) | scalar in the range [0,1]
Specific humidity, defined as the mass fraction of water vapor in a moist air mixture, at the inlet of the external fluid side of the evaporator during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
and
Inlet humidity specification to
Specific humidity
.
Nominal inlet water vapor mole fraction — Mole fraction of water vapor at the inlet
0.01
(default) | scalar in the range [0,1]
Mole fraction of the water vapor in a moist air mixture at the inlet of the external fluid side of the evaporator during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
and
Inlet humidity specification to
Mole fraction
.
Nominal inlet humidity ratio — Humidity ratio at inlet
0.01
(default) | scalar in the range [0,1]
Humidity ratio, defined as the mass ratio of water vapor to dry air and trace gas, at the inlet of the external fluid side of the evaporator during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
and
Inlet humidity specification to
Humidity ratio
.
Nominal inlet wet-bulb temperature — Wet-bulb temperature at the start of simulation
287 K
(default) | positive scalar in the range [0,1]
Evaporator wet-bulb temperature in a moist air mixture at the inlet of the external fluid side of the evaporator during the nominal operating condition.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
and
Inlet humidity specification to
Wet-bulb temperature
.
Inlet trace gas specification — Method to describe trace gas level at inlet
Mass fraction
(default) | Mole fraction
Method the block uses to describe the trace gas level at the external fluid side inlet of the evaporator during the nominal operating condition.
Nominal inlet trace gas mass fraction — Mass fraction of trace gas at inlet
0.001
(default) | scalar in the range [0,1]
Mass fraction of the trace gas in a moist air mixture at the inlet of the external fluid side of the evaporator during the nominal operating condition.
The block ignores this parameter if the Trace gas
model parameter in the Moist Air
Properties (MA) block is
None
.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Moist
air
and Inlet trace gas
specification to Mass
fraction
.
Nominal inlet trace gas mole fraction — Mole fraction of trace gas at inlet
0.001
(default) | scalar in the range [0,1]
Mole fraction of the trace gas in a moist air mixture at the inlet of the external fluid side of the evaporator during the nominal operating condition.
The block ignores this parameter if the Trace gas
model parameter in the Moist Air
Properties (MA) block is
None
.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Moist
air
and Inlet trace gas
specification to Mole
fraction
.
External fluid volume — Volume of fluid in evaporator
0.1
m^3
(default) | positive scalar
Total volume of external fluid in the evaporator.
Cross-sectional area at port Ae — Flow area at port Ae
0.01
m^2
(default) | positive scalar
Flow area at the evaporator external fluid port Ae.
Cross-sectional area at port Be — Flow area at port Be
0.01
m^2
(default) | positive scalar
Flow area at the evaporator external fluid port Be.
Evaporator wall thermal mass — Option to model evaporator wall heat transfer
Off
(default) | On
Whether to include the temperature dynamics of the heat transfer surface.
Evaporator wall mass — Evaporator heat transfer mass
1
kg
(default) | positive scalar
Total mass of the evaporator heat transfer surface.
Dependencies
To enable this parameter, select Evaporator wall thermal mass.
Evaporator wall specific heat — Specific heat of evaporator transfer surface
490
J/(K*kg)
(default) | positive scalar
Specific heat of the evaporator heat transfer surface.
Dependencies
To enable this parameter, select Evaporator wall thermal mass.
Initialize to nominal operating conditions — Whether to specify evaporator initial conditions
On
(default) | Off
Whether to start the simulation at the nominal operating condition or specify a different set of initial conditions using additional parameters.
Initial pressure — Fluid pressure at start of simulation
0.101325
MPa
(default) | positive scalar
Evaporator external fluid pressure at the start of the simulation.
Dependencies
To enable this parameter, clear the Initialize to nominal operating conditions check box.
Initial fluid energy specification — Initial state of the evaporator external fluid
Specific enthalpy
(default) | Temperature
| Vapor quality
| Vapor void fraction
| Specific internal energy
Quantity used to describe the initial state of the evaporator external fluid.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
and clear the Initialize to
nominal operating conditions check box.
Initial temperature — Temperature at start of simulation
293.15
K
(default) | positive scalar | two-element vector
Temperature at the start of simulation. If the value is a scalar, then the block assumes that the initial temperature is uniform. If the value is a two-element vector, then the block assumes that the initial temperature varies linearly between the ports evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set either:
External fluid for evaporator heat transfer to
Moist air
orThermal liquid
and clear the Initialize to nominal operating conditions check box.External fluid for evaporator heat transfer to
Two-phase fluid
, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification toTemperature
.
Initial vapor quality — Vapor mass fraction at start of simulation
0.5
(default) | scalar in the range [0,1] | two-element vector
Evaporator external fluid vapor quality, defined as the mass fraction of vapor in a liquid-vapor mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial vapor quality is uniform. If the value is a two-element vector, then the block assumes that the initial vapor quality varies between the evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
, clear the Initialize to nominal
operating conditions check box, and set
Initial fluid energy specification to
Vapor quality
.
Initial vapor void fraction — Vapor volume fraction at start of simulation
0.5
(default) | scalar in the range [0,1] | two-element vector
Evaporator external fluid vapor void fraction, defined as the volume fraction of vapor in a liquid-vapor mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial vapor void fraction is uniform. If the value is a two-element vector, then the block assumes that the initial vapor void quality varies between the evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
, clear the Initialize to nominal
operating conditions check box, and set
Initial fluid energy specification to
Vapor void fraction
.
Initial specific enthalpy — Enthalpy per unit mass at start of simulation
1500
kJ/kg
(default) | positive scalar | two-element vector
Evaporator external fluid specific enthalpy at the start of simulation. If the value is a scalar, then the block assumes that the initial specific enthalpy is uniform. If the value is a two-element vector, then the block assumes that the initial specific enthalpy varies between the evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
, clear the Initialize to nominal
operating conditions check box, and set
Initial fluid energy specification to
Specific enthalpy
.
Initial specific internal energy — Internal energy per unit mass at start of simulation
1500
kJ/kg
(default) | positive scalar | two-element vector
Evaporator external fluid specific internal energy at the start of simulation. If the value is a scalar, then the block assumes that the initial specific internal energy is uniform. If the value is a two-element vector, then the block assumes that the initial specific internal energy varies between the evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Two-phase
fluid
, clear the Initialize to nominal
operating conditions check box, and set
Initial fluid energy specification to
Specific internal energy
.
Initial humidity specification — Method used to describe initial humidity level
Relative humidity
(default) | Specific humidity
| Mole fraction
| Humidity ratio
| Wet-bulb temperature
Method used to describe the initial humidity level in evaporator external fluid.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Moist
air
and clear the Initialize to nominal
operating conditions check box.
Initial relative humidity — Relative humidity at start of simulation
0.5
(default) | scalar in the range [0,1] | two-element vector
Evaporator external fluid relative humidity at the start of simulation. If the value is a scalar, then the block assumes that the initial relative humidity is uniform. If the value is a two-element vector, then the block assumes that the initial relative humidity varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
,
clear the Initialize to nominal operating
conditions check box, and set Initial
humidity specification to Relative
humidity
.
Initial specific humidity — Specific humidity at start of simulation
0.01
(default) | scalar in the range [0,1] | two-element vector
Evaporator external fluid specific humidity, defined as the mass fraction of water vapor in a moist air mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial specific humidity is uniform. If the value is a two-element vector, then the block assumes that the initial specific humidity varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
,
clear the Initialize to nominal operating
conditions check box, and set Initial
humidity specification to Specific
humidity
.
Initial water vapor mole fraction — Mole fraction of water vapor at start of simulation
0.01
(default) | scalar in the range [0,1] | two-element vector
Mole fraction of the water vapor in the evaporator external fluid at the start of simulation. If the value is a scalar, then the block assumes that the initial water vapor mole fraction is uniform. If the value is a two-element vector, then the block assumes that the initial water vapor mole fraction varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
,
clear the Initialize to nominal operating
conditions check box, and set Initial
humidity specification
Mole fraction
.
Initial humidity ratio — Humidity ratio at start of simulation
0.01
(default) | scalar in the range [0,1] | two-element vector
Evaporator external fluid humidity ratio, defined as the mass ratio of water vapor to dry air and trace gas, at the start of simulation. If the value is a scalar, then the block assumes that the initial humidity ratio is uniform. If the value is a two-element vector, then the block assumes that the initial humidity ratio varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
,
clear the Initialize to nominal operating
conditions check box, and set Initial
humidity specification
Humidity ratio
.
Initial moist air wet-bulb temperature — Wet-bulb temperature at the start of simulation
287 K
(default) | positive scalar in the range [0,1]
Wet-bulb temperature at the start of the simulation. The block uses this value to calculate humidity.
If the value is a scalar, then the block assumes that the initial wet-bulb temperature is uniform. If the value is a two-element vector, then the block assumes that the initial wet-bulb temperature varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
,
clear the Initialize to nominal operating
conditions check box, and set Initial
humidity specification to Wet-bulb
temperature
.
Initial trace gas specification — Method to describe initial trace gas level
Mass fraction
(default) | Mole fraction
Method used to describe the trace gas level at the start of simulation.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Moist
air
and clear the Initialize to nominal
operating conditions check box.
Initial trace gas mass fraction — Mass fraction of trace gas at start of simulation
0.001
(default) | scalar in the range [0,1] | two-element vector
Mass fraction of trace gas in a moist air mixture at the start of simulation. If the value is a scalar, then the block assumes that the initial mass fraction is uniform. If the value is a two-element vector, then the block assumes that the initial mass fraction varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
The block ignores this parameter if the Trace gas
model parameter in the Moist Air
Properties (MA) block is
None
.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
,
clear the Initialize to nominal operating
conditions check box, and set Initial trace
gas specification to Mass
fraction
.
Initial trace gas mole fraction — Mole fraction of trace gas at start of simulation
0.001
(default) | scalar in the range [0,1] | two-element vector
Mole fraction of the trace gas in a moist air mixture at the start of simulation. If the value is a scalar, then the block assumes that the initial mole fraction is uniform. If the value is a two-element vector, then the block assumes that the initial mole fraction varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.
The block ignores this parameter if the Trace gas
model parameter in the Moist Air
Properties (MA) block is
None
.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist air
,
clear the Initialize to nominal operating
conditions check box, and set Initial trace
gas specification to Mole
fraction
.
Initial mass ratio of water droplets to moist air — Ratio of water droplets to moist air
0
(default) | positive scalar
Initial mass ratio of water droplets to moist air.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Moist
air
and clear the Initialize to nominal
operating conditions check box.
Initial evaporator wall temperature — Evaporator surface temperature at simulation start
293.15
K
(default) | positive scalar | two-element vector
Heat transfer surface temperature at the start of simulation. If it this value is a scalar, the block assumes that the initial temperature is uniform. If this value is a two-element vector, then the block assumes that the temperature varies linearly between ports Ae and Be with the first element corresponding to Ae and second element corresponding to Be.
Dependencies
To enable this parameter, clear the Initialize to nominal operating conditions and Evaporator wall thermal mass check boxes.
Relative humidity at saturation — Relative humidity point of condensation
1
(default) | nonnegative scalar
Relative humidity point of condensation. Condensation occurs above this value. In most cases, this value is 1, which is equivalent to 100%. A value greater than 1 indicates a supersaturated vapor.
Dependencies
To enable this parameter, set External fluid for evaporator heat
transfer to Moist
air
.
Water vapor condensation time constant — Time scale for condensation
1e-3 s
(default) | positive scalar
Characteristic time scale at which an oversaturated moist air volume returns to saturation by condensing out excess humidity.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Moist
air
.
Water droplets evaporation time constant — Time scale for evaporation
1e-3 s
(default) | positive scalar
Characteristic time scale at which water droplets evaporate to vapor.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Moist
air
.
Fraction of condensate entrained as water droplets — Fraction of condensate in water droplets
1
(default) | scalar in the range [0,1]
Fraction of the condensate in the moist air that is entrained as water droplets.
Dependencies
To enable this parameter, set External fluid for
evaporator heat transfer to Moist
air
.
Correlation Coefficients
Modify condenser Nusselt number correlation coefficients — Whether to modify condenser Nusselt number correlation
coefficients
Off
(default) | On
Whether to manually modify the condenser Nusselt number correlation coefficients. Select this parameter to adjust the off-design performance of the condenser.
a in Nu = a*Re^b*Pr^c for refrigerant, liquid regime — Correlation coefficient for refrigerant subcooled liquid
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for a subcooled liquid for the condenser. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify condenser Nusselt number correlation coefficients.
a in Nu = a*Re^b*Pr^c for refrigerant, mixture regime — Correlation coefficient for refrigerant liquid-vapor mixture
0.005
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the liquid-vapor mixture for the condenser. The default value is based on the Cavallini and Zecchin correlation.
Dependencies
To enable this parameter, select Modify condenser Nusselt number correlation coefficients.
a in Nu = a*Re^b*Pr^c for refrigerant, vapor regime — Correlation coefficient for refrigerant superheated vapor
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the superheated vapor for the condenser. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify condenser Nusselt number correlation coefficients.
b in Nu = a*Re^b*Pr^c for refrigerant — Reynolds number exponent in correlation for refrigerant
0.8
(default) | positive scalar
Reynolds number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the condenser refrigerant. The same value applies to subcooled liquid, liquid-vapor mixture, and superheated vapor.
Dependencies
To enable this parameter, select Modify condenser Nusselt number correlation coefficients.
c in Nu = a*Re^b*Pr^c for refrigerant — Prandtl number exponent in correlation for refrigerant
0.33
(default) | positive scalar
Prandtl number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for condenser refrigerant. The same value applies to subcooled liquid, liquid-vapor mixture, and superheated vapor.
Dependencies
To enable this parameter, select Modify condenser Nusselt number correlation coefficients.
a in Nu = a*Re^b*Pr^c for external fluid, liquid regime — Correlation coefficient for subcooled liquid in two-phase fluid
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the subcooled condenser external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify condenser
Nusselt number correlation coefficients and set
External fluid for condenser heat transfer
to Two-phase fluid
.
a in Nu = a*Re^b*Pr^c for external fluid, mixture regime — Correlation coefficient for liquid-vapor mixture in two-phase fluid
0.005
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for liquid-vapor mixture in the condenser external fluid. The default value is based on the Cavallini and Zecchin correlation.
Dependencies
To enable this parameter, select Modify condenser
Nusselt number correlation coefficients and set
External fluid for condenser heat transfer
to Two-phase fluid
.
a in Nu = a*Re^b*Pr^c for external fluid, vapor regime — Correlation coefficient for superheated vapor in two-phase fluid
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for superheated vapor in the condenser external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify condenser
Nusselt number correlation coefficients and set
External fluid for condenser heat transfer
to Two-phase fluid
.
a in Nu = a*Re^b*Pr^c for external fluid — Correlation coefficient for condenser external fluid
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the condenser external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify condenser
Nusselt number correlation coefficients and set
External fluid for condenser heat transfer
to Moist air
or Thermal
liquid
.
b in Nu = a*Re^b*Pr^c for external fluid — Reynolds number exponent in correlation for condenser external fluid
0.8
(default) | positive scalar
Reynolds number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the condenser external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify condenser Nusselt number correlation coefficients.
c in Nu = a*Re^b*Pr^c for external fluid — Prandtl number exponent in correlation for condenser external fluid
0.33
(default) | positive scalar
Prandtl number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the condenser external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify condenser Nusselt number correlation coefficients.
Modify evaporator Nusselt number correlation coefficients — Whether to modify evaporator Nusselt number correlation coefficients
Off
(default) | On
Whether to manually modify the evaporator Nusselt number correlation coefficients. Select this parameter to adjust the off-design performance of the evaporator.
a in Nu = a*Re^b*Pr^c for refrigerant, liquid regime — Correlation coefficient for refrigerant subcooled liquid
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for a subcooled liquid for the evaporator. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.
a in Nu = a*Re^b*Pr^c for refrigerant, mixture regime — Correlation coefficient for refrigerant liquid-vapor mixture
0.005
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the liquid-vapor mixture for the evaporator. The default value is based on the Cavallini and Zecchin correlation.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.
a in Nu = a*Re^b*Pr^c for refrigerant, vapor regime — Correlation coefficient for refrigerant superheated vapor
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the superheated vapor for the condenser. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.
b in Nu = a*Re^b*Pr^c for refrigerant — Reynolds number exponent in correlation for refrigerant
0.8
(default) | positive scalar
Reynolds number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the evaporator refrigerant. The same value applies to subcooled liquid, liquid-vapor mixture, and superheated vapor.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.
c in Nu = a*Re^b*Pr^c for refrigerant — Prandtl number exponent in correlation for refrigerant
0.33
(default) | positive scalar
Prandtl number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for evaporator refrigerant. The same value applies to subcooled liquid, liquid-vapor mixture, and superheated vapor.
Dependencies
To enable this parameter, select External fluid for evaporator heat transfer.
a in Nu = a*Re^b*Pr^c for external fluid, liquid regime — Correlation coefficient for subcooled liquid in two-phase fluid
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the subcooled evaporator external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation
coefficients and set External fluid for
evaporator heat transfer to Two-phase
fluid
.
a in Nu = a*Re^b*Pr^c for external fluid, mixture regime — Correlation coefficient for liquid-vapor mixture in two-phase fluid
0.005
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for liquid-vapor mixture in the evaporator external fluid. The default value is based on the Cavallini and Zecchin correlation.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation
coefficients and set External fluid for
evaporator heat transfer to Two-phase
fluid
.
a in Nu = a*Re^b*Pr^c for external fluid, vapor regime — Correlation coefficient for superheated vapor in two-phase fluid
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for superheated vapor in the evaporator external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation
coefficients and set External fluid for
evaporator heat transfer to Two-phase
fluid
.
a in Nu = a*Re^b*Pr^c for external fluid — Correlation coefficient for evaporator external fluid
0.023
(default) | positive scalar
Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the evaporator external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation
coefficients and set External fluid for
evaporator heat transfer to Moist
air
or Thermal
liquid
.
b in Nu = a*Re^b*Pr^c for external fluid — Reynolds number exponent in correlation for evaporator external fluid
0.8
(default) | positive scalar
Reynolds number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the evaporator external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.
c in Nu = a*Re^b*Pr^c for external fluid — Prandtl number exponent in correlation for evaporator external fluid
0.33
(default) | positive scalar
Prandtl number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the evaporator external fluid. The default value is based on the Colburn equation.
Dependencies
To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.
Version History
Introduced in R2023aR2024b: Model water droplets suspended in moist air flow
Blocks in the moist air domain can now model water droplets suspended in a moist air flow. To enable droplet tracking, select Enable entrained water droplets in the Moist Air Properties (MA) block connected to your moist air network.
R2024a: New moisture specification option
The block has new options for the Inlet humidity specification and
Initial humidity specification parameters for both the
condenser and evaporator external fluids. This option, called Wet-bulb
temperature
, allows you to input data in the form of a wet-bulb
temperature.
MATLAB 명령
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